Containers for microwavable materials, particularly foodstuffs, have enjoyed increased marketing demand in recent times. The basic requirements for a microwavable container include high temperature resistance and adequate stiffness at elevated temperatures. Additionally, the outer surface should remain sufficiently cool such that the container may be safely handled.
Since most polymers having the necessary stiffness typically become quite hot when in contact with a heated foodstuff, it has previously been suggested to provide containers formed of laminates having an outer, insulating layer. For example, it has previously been suggested that a microwavable food packaging container be formed as a laminate with a polyethylene terephthalate film laminated on the interior of a foamed polystyrene sheet. The foamed polystyrene sheet material provides good heat insulation allowing such containers to be safely handled after microwaving. It has also been suggested to laminate other insulators, such as cardboard, to polymers to provide a safe, cool outer protective layer to microwavable containers. Alternatively, the use of a container having a core layer of a foamed thermoplastic polymeric material such as high density polyethylene or polypropylene laminated to surface layers of polyethylene terephthalate or polypropylene has also been suggested.
A significant disadvantage of previously known microwavable containers such as those discussed above lies in the difficulty in recycling laminates of different materials. Since these materials inherently have different requirements for recycling, it is desirable to first separate the layers prior to recycling. Such separating is very difficult and costly, making it impractical on a commercial scale. It would, therefore, be very desirable to provide a microwavable container having the desirable properties referred to above and which has components which are readily separable for recycling.
Another disadvantage of previously known recyclable microwavable containers is the consumer's perception of overpackaging when a container is made up of multiple components. It would, therefore, be very desireable to provide a microwavable container which avoids the consumer's perception of multiple components while simultaneously providing components which are readily separable for recycling.